Korean Patent Publication No. 2010-0061538 discloses technology of supplying fuel and a diluted solution in a secondary combustion zone downstream of a primary combustion zone of a combustion engine. The technology performs secondary combustion that assists combustion taking place in the primary combustion zone by providing a manifold on a wall that surrounds the secondary combustion zone, locating an injector nozzle in the manifold, and injecting the fuel in the secondary combustion zone. Although the technology may reduce the amount of fuel injected in the secondary combustion zone, there is no interaction between the combustion in the primary combustion zone and the combustion in the secondary combustion zone. That is, combustion performance in the primary combustion zone is not improved by fuel injection in the secondary combustion zone.
U.S. Pat. No. 4,389,848 discloses a structure in which a fuel injector includes a primary nozzle located on the upstream side of a burner and a secondary nozzle located on the downstream side and fuel and air are recirculated by injecting the fuel through the secondary nozzle. However, in this structure, since the secondary nozzle is located on an extension of the central axis of the primary nozzle of the burner, recirculation effect of the fuel and the air is not sufficient.
(Patent Document 1) Korean Patent Publication No. 2010-0061538 (Jun. 7, 2010)
(Patent Document 2) U.S. Pat. No. 4,389,848 (Jun. 28, 1983)